The present invention relates to a method for the production of a coating and a workpiece coated by the method.
The application of a ceramic layer of oxides, nitrides, oxynitrides, and carbides on a workpiece (substrate) is known from Swiss CH-P 664 163. In the known method, a low-voltage arc is used to evaporate an oxide or nitride former which is held in a crucible in a vacuum chamber, and with a nitrogen or oxygen atmosphere in the chamber. The workpiece is electrically insulated on a holder. Due to the electrical gas discharge maintained during the operation of the installation, the holder with the workpieces was charged to a negative potential during the condensation of the vapor with the effect that positive ions are accelerated from the active vapor and the residual gas (plasma) toward the workpieces.
A further method for applying a ceramic boron nitride layer is known from the publication by K. Inagawa et al., "Preparation of cubic boron nitride film by activated reactive evaporation with a gas activation nozzle", J. Vac. Sci. Technol. A 5 (4), Jul/Aug. 1987, pp. 2696-2700. A positive potential is applied to a gas inlet opening in order to activate the reactive gas used for the generation of the ceramic layer. Further an ac voltage in the ten megahertz range is applied to the workpieces in order to accelerate the ions of the introduced gas toward the workpieces.
With the known method it is possible to apply insulating layers onto conducting layers. It is also possible to apply insulating layers onto only electrically insulated substrates, however, the capacity of adherence is less than desirable. If the workpieces are worked with an ac bias voltage then a sufficiently high-frequency shielding of the installation must be ensured; likewise the terminating wave impedance which changes with the shape, size and number of the work-pieces, must be matched in a time-consuming procedure to that of the generator for generating the ac voltage.